Only recently has attention been paid to the initiation of responses of human polymorphonuclear leukocytes (PMN) and to biochemical and physiological events which take place during the first minute of granulocyte stimulation. Measurements of these earliest events and determinations of the order in which they occur allow a separation of causes from effects. By use of techniques which provide a time resolution measured in seconds (rather than minutes), we have established a temporal order for membrane hyperpolarization, cAMP changes, lysosomal enzyme release, and superoxide anion generation. Our objectives are to place these and the following studies into an explanatory framework which would permit a logical description of how surface ligand interactions are translated into cellular responses: 1) What is the role of transient elevations in cellular cAMP which accompany surface stimulation of PMN? 2) Is protein carboxymethylation a critical step in PMN responses? 3) Is protein calmodulin critical in PMN responses? 4) To what extent are rapid changes in membrane-bound calcium and magnesium important during stimulation?